Method and apparatus for printing cylindrical objects



Feb. 9, 1960 e. F. SCOTT 2,924,169

METHOD AND APPARATUS FOR PRINTING CYLINDRICAL OBJECTS Filed Sept. 6, 1955 5 Sheets-Sheet l INSULA TOR r0 CENTER :ucmooemssmau WASH AND UNLOAD/NG GLAZE AIR BLAST STAT/0N SPRAY gig 3g r HEATER PRINTER HEATER "ll INVENTOR ATTORNEY Feb. 9, 1960 G. F. SCOTT 2,924,159.

METHOD AND APPARATUS FOR PRINTING CYLINDRICAL OBJECTS Filed Sept. 6, 1955 5 Sheets-Sheet 2 INVENTOR ATTORNEY Feb. 9,. 1960 s. F. SCOTT 2,924,169

METHOD AND APPARATUS FOR PRINTING CYLINDRICAL OBJECTS Filed Sept. 6, 1955 5 Sheets-Sheet 5 ATTORNEY V Feb. 9, 1960 METHOD AND APPARATUS FOR PRINTING CYLINDRICAL OBJECTS Filed Sept. e, 1955 5 Sheets-Sheet 5 fiz f c off ATTORNEY United States Patent METHDD AND APPARATUS FOR PRINTING CYLINDRICAL OBJECTS Guy F. Scott, Ferndale, Mich., assignor to General Motors Corporation, Detroit, Mich, a corporation of Delaware Application September 6, 1955, Serial No. 532,500

2 Claims. (Cl. 101-40) This invention relates to a method and apparatus for printing cylindrical objects, and more particularly to a method and apparatus for printing such objects as they move continuously past the printer.

Technology is continuously searching for methods and means for improving processing techniques as a result of the pressure of ever increasing competition and a constant demand for a low-priced product as good as or better than that available. This is especially important in those instances in which the product being worked on is mass produced, as in the manufacture of spark plugs and containers of various types.

It has been common practice in performing a printing operation on such objects as spark plug insulators and cylindrical containers to position the objects on a plurality of work-holding stations, each station being brought in turn into a stationary position relative to the printer so as to enable the device being printed to be rotated and coated by the ink carrying engraved plates. Upon completion of the printing operation on each object, the mechanism mounting the work-holding stations is indexed to bring the next following station into stationary printing position.

Obviously, such intermittent indexing methods are unsatisfactory where high production is required since the inertia of the indexing operation places an inherent limit on the rate of printing. Likewise, such printing machines are generally expensive in initial cost and in maintenance by reason of the indexing and timer control mechanism, generally eiectro-mechanical in nature, required.

It is therefore an object of my invention to provide a simple and inexpensive method for printing cylindrical objects as they move continuously past the printing station. It is another object of my invention to provide a method whereby spark plug insulators may be continuously printed. It is another object of my invention to provide a device adapted to print cylindrical objects as they move past the printing station. It is another object of my invention to provide a printer adapted for ready adjustment to enable the coating of cylindrical objects of different diameters as they move continuously past the printer. It is another object of my invention to provide a device adapted to print spark plug insulators as they move without interruption through the printing station.

These and other objects of my invention are achieved by bringing a resilient printing pad into contact with a rotatable cylindrical object in such a manner as to maintain the pad under compression as its printing surface passes over the surface of the object moving continuously through the printing station, means being provided ICC for the ready control of the length of travel of the object while maintaining the pad under compression.

A preferred embodiment of the method and means of my invention is shown on the accompanying drawings in which Figure 1 is a block diagram showing the sequence of operations employed in printing and preparing a spark plug insulator for glazing; Figure 2 is a side view of the printer and conveyor frame; Figure 3 is a front view of the printer and conveyor frame showing one insulator and carrier in printing position; Figure 4 is a plan view of the frame and printer 'base showing the printing wheel in shadow outline along with the carrier assemblies and carrier pin speed control; Figure 5 is an enlarged cross-sectional view of the printer taken on line 5-5 of Figure 3 showing the insulator and the carrier assembly in printing position; Figure 6 is an enlarged cross-sectional view taken on line 6-6 of Figure 2 showing the details of construction of the adjustable anvil; Figure 7 is an enlarged broken away view showing the details of construction of the printer blanket adjusting mechanism; and Figure 8 is an enlarged partial view in perspective of the carrier assembly and carrie pin speed control threadmill.

Having reference now to the drawings, more particularly to Figure 1, there is shown a schematic diagram .for the continuous processing of spark plug insulators through the printing and glaze application stations preparatory to the glazing and electrode assembly operations. The spark plug insulators are each positioned on a carrier pin secured to a conveyor belt which then progresses the insulators through a heating station to raise the temperature of the insulators to approximately F. in

order that the printing ink might dry rapidly and thus prevent the colors and/ or design from running together. The heated insulators are then carried through the printing station in continuous movement while at the same time rotating and taking the inked image from the printer wheel. The insulators then progress through a second heater to raise the temperature thereof to approximately 300 F. in order to rapidly dry the glaze slurry which is applied at the next succeeding station by means of any suitable mechanism such as spray applicators. The sprayed insulators are then unloaded and the conveyor belt moves through a wash and air blast station which serves to clean and dry the carrier pins preparatory to repeating the described cycle of operations. The cleaning operation is necessary in the handling of spark plug insulators in order to minimize the extent of wear of the carrier pins due to rotation of the insulators on the pin during the printing operation as is more fully described hereinafter.

Having particular reference to the printer station, there is shown in Figures 2, 3 and 4 a side, front and plan view, respectively, of such station. As shown in the drawings, the station comprises a printer I mounted on a base 3 which is in turn mounted in fixed' relationship with and on a frame 5, shown as triangular on its ends and being suitably braced for strength. As is clearly with respect to frame 5 in a manner fully described hereinafter. i

As is shown somewhat diagrammatically in Figure 2 and more clearly in Figure 3, the printer 1 comprises a support or housing 7 on which there are positioned the desired number of engraved plate cylinders and ink fountains 9, shown in the embodiment in my invention as being two in number. Any suitable ink fountainplate cylinder construction may be used, these features beingwell known in the art and forming no part of my invention. Cooperating with the plate cylinders is a printing wheel 11 on which there are mounted the desired number of printing pads 13. As the pads 13 rotate by the plate cylinders, which are rotating at the same peripheralspeed as the pads, the image is transferred from the engraved plates on the plate cylinders to the pads. The printer 1 shown in my preferred embodiment is equipped with a pair of inking fountains and plate cylinders in order to print upon the spark plug insulators with a two-color design. Obviously, one or more such units may be used dependent solely on the number of colors desired. Likewise, though the printing wheel of my preferred embodiment is provided with two printing pads positioned 180 apart on the periphery thereof, one or more such pads may be used.

As is clearly shown in Figures 3 and 7, the construction of the printing wheel 11 is such as to enable simple and ready adjustment of the printing pads 13 in order to permit their proper location on the wheel for the correct placement of the image on the insulators. As shown, the wheel .11 consists of four equally spaced sectors 15 with a single pair of oppositely arranged sectors serving as the printing pad support members. As is more clearly shown in Figure 5, the printing pads 13 are formed of a resilient rubber or rubber-like material such as neoprene or chloroprene or other suitable materials capable of being subjected to repeated compression and the effects of various chemical dyes and inks without unduly rapid deterioration. The pads 13 are glued or otherwise secured to blankets 17 stretched over the peripheral surface of thepair of oppositely disposedsectors 15, the blankets being formed of any suitable material such as rubber, leather, or cloth. Adjustment of the position of the printing pads 13 on the sectors 15 is achieved by rolling one or another of the ends of the blankets 17 upon roller 19 to which each end is secured. The roller 19 is positioned between adjacent sectors 15 by means of end plates 23 on each of which there is mounted a rachet 25 and pawl 27 for locking the blankets in adjusted position.

A motor 29 is mounted upon the base member 3 and serves as' the main source of power for the printer and for the conveyor belt. As is conventional in the art, and thus'forms no part of my invention, the motor 29 drives the plate'cylinders and the printing wheel 11 through a series of gear reduction units positioned on the support 7. The wheel 11 rotates at such speed as to makeone-half a revolutionper carrier passing through the printing station;

Correspondingly, where the printing wheel 11 is provided with three or four printing pads, the wheel will rotate at such speed as to make one-third or one-fourth revolution per carrier. By way of example, as in the embodiment shown on the drawings, where the carriers attached to the continuous conveyor belt move under the printing wheel 11 at a rate of 70 carriers per minute, the printer wheel rotates at 35 r.p.m. By driving the printer wheel and the conveyor belt by chain belts from the same drive motor 29, perfect synchronization is assured between the wheel and the carriers secured to the conveyor belt.

As is clearly shown in Figures 4, 5, 6 and 8, a plurality of carriers 31. are spaced apart on, preferably equidistantly, and are securely attached to a conveyor belt or a continuous roller chain 33 by means of a pair of mounting brackets 35. The conveyor belt 33 moves the carriers 31 through the printing station at a constant rate-of speed without hesitating or indexing, as is conventional in current practice, and is so synchronized with the printing wheel 11 that each pad 13 is on the bottom of the wheel .at the same time that the insulator 2 or other cylindrical object, is directly under the wheel centerline. As is shown in Figures 3 and 6, the carriers 31 are supported on a track 34 secured to the frame 5, the track being formed of any suitable material such as nylon, steel or any other suitable material. The track 34 is provided with front and rear guide walls 36 to keep the carriers 31 in line.

This is especially important as the carriers 31 move through the printing station in order to properly locate the image on the insulators.

I have discovered that the entire image on each printing pad 13 may be transferred to the surface of the in-.

sula'tor' 2 as it moves continuously through the printing station by maintaining the insulator in contactwith the pad for a small but sufficient distance to enable the entire printing surface of the pad to roll out on the insulator as it travels through the printing station. It is of course apparent that the insulator 2 rotates at the same peripheral speed as does the printing pad in order not to distort and smear the image being transferred.

As noted above, the wheel 11 and the carriers 31 are so synchronized that the pads 13 are at the bottom of the r r wheel at the same time that each insulator 2 and its supporting carrier 31 are directly under the centerline of the wheel. 7 Inasmuch as it is necessary to place the rubber pads 13 under compression during the printing operation, a vertical adjustable anvil 37 is positioned directly under the centerline of the wheel 11 in order to support the carriers 31 such a distance from the printing pad surface in its lowermost position as to place the insulator into contact with the pad at a predetermined distance ahead of the centerline and maintain contact therewith until contact is broken at substantially the same distance behind the centerline. It should be understood that in using the term "ce'nt'erline I have reference to a radial line subs'ta'ntially perpendicular to the chordal line generated by the insulator surface as it rolls over the pad.

As is clearlyshown in Figure 6, the adjustable anvil comprises a support head 39 having secured to its upper surface a carrier support41 shown clearly. in Figure 5 as two spaced apart strips of wear resistant material such.

as nylon, steel or other suitable material. It will be noted that the carrier support 41 and the upstream edge of the niain carrier support track 34 adjacent thereto are tapered downwardly in order that each carrier 31 may ride smoothly onto the support sections whether or not the surface of the carrier support 41 is above or below the surface of the main track section. An adjusting screw 43 having a knurled operating member 45 secured to its outer end.

nels 53 on the frame 5. It is thus readily apparent that by threading the screw 43 into and out of the block 51, the carrier support 41 is eitherraised or lowered to control both the degree of compression of the printing pads 13 and the transverse distance through which the insulator 2 moves while receivirig the inked impression from the pad.

Though the insulator 2 will be rotated by the printing pad'at the same peripheral speed as that of the pad when the image is being transferred to it, it was found to be desirable to bring the carrier pin' 55 upon which the insulator is slidably. mounted into rotation in order to attain an insulatorperipher'al s'peedsubstahtially the same as the peripheral of the printing pads 13 on the wheel 11 prior to bringing the insulator into contact with the printing pad. I have found this to be desirable in order to prevent smearing of the ink due to the inertia of the insulator on first being contacted by the printing pad and in order to substantially eliminate undue wear of the carrier pin by the insulator.

As is clearly shown in Figures 4, 5 and 8, I bring the insulator 2 up to the desired speed by rotating the pin 55 upon which it is mounted. At the rear of the carrier pin 55, there is positioned a sprocket 57 which contacts a roller chain threadmill 59 just before reaching the printing position. As is shown on the drawings, the threadmill 59 comprises a triple-strand chain drive 61 driven endlessly between a pair of double sprockets 63, each pair of sprockets cooperating with the inner and outer strands while the carrier sprocket 57 cooperates with the middle strand. As is clearly shown in Figure 5, carrier pin 55 is rotatably supported within the carrier block 65 by means of a pair of ball bearings 67 positioned at the front and rear of each carrier block. A supporting pin 69 is removably clamped on the front end of the bearing supported shaft 71 by means of the threaded locking nut 73. In this manner, the carrier 31 may be readily adapted to retain cylindrical objects of various sizes and internal shapes by merely changing supporting pins 69.

The speed of the threadmill 59 is controlled by means of any suitable variable speed drive mechanism well known in the art such as the Reeves drive assembly 75 shown clearly in Figures 3 and 4. By means of such variable speed drive mechanism, the insulator 2 is already revolving at substantially the same peripheral speed as the printing pads 13 at their point of contact. Any minor variation in peripheral speed between the insulator 2 and the printing pads 13 is automatically adjusted inasmuch as the frictional force between the printing pad and the insulator is greater than that between the insulator and the supporting pin 69 with the result that the insulator slips around the carrier pin. Minor variations in peripheral speed may result from slip in or inaccurate setting of the drive mechanism, variation in the outside diameter of the insulators being printed or stretch in the drive chain 61 without compensating for such increase in chain length by increasing the speed of the drive mechanism.

Inasmuch as the printing pads 13 are placed under compression by the insulators 2 during the printing operation and since the carriers 31 are freely supported on the track 34 and carrier supports 41, I have found it necessary to provide suitable means for retaining the carrier on the carrier supports. As is clearly shown in Figure 5, I have provided a spring-loaded plunger 77 having a bearing 79 mounted on the lower end thereof with its axis substantially parallel to that of the carrier pin 55 as it is moved through the printing station. As is shown on the drawing, the plunger 77 is positioned within a housing 80 suitably mounted on the frame 5.

As has been previously stated, and as is clearly shown in Figure 2, the printer 1 is adjustably mounted on the base 3 in order to permit the printer to be adjusted relative to the frame 5 and the carriers 31 in both a front to rear and side to side direction. Adjustment from front to rear is necessary in order to properly locate the printing pads on the surface of the insulators, such location being dependent upon the length and shape of the insulators. Likewise, side to side adjustment may be required in order to compensate for stretch of the conveyor chain 33 and thus maintain the insulators 2 in contact with the pad 13 over the proper length of travel. These adjustments are made possible by mounting the printer 1 on a pair of overlying plates, each being independently slidable between a pair of guide tracks positioned at right angles to each other.

Front and rear adjustment is made possible by loosening the bolts 81 passing through slots 83 extending in a front to rear direction in each of the four corners of adjusting plate 85. The bolts 81 serve to secure the plate on the upper surface of plate 87. Likewise, the plate 85 is slidable between guide tracks 89 secured on plate 87 and extending from front to rear thereof. The printer 1 is locked in its front to rear adjusted position by any suitable means shown in Figures 2 and 4 as being a pair of locating bolts 91 threadedly positioned within blocks 93 which are secured to the plate 87 at the front and rear thereof. As shown on the drawings, the bolts 91 bear against the front and rear edges of plate 85 and are locked in such position by means of locking nuts 95. Side to side adjustment is made possible by a similar combination of elements. The printer 1 is secured through bolts 81 and plate 85 to plate 87. The plate 87 is adjustable between guide tracks 97 secured to an anchor plate 99 and extending in a direction at right angles to guide tracks 89. The plate 87 is adjustably secured to the anchor plate 99 in a manner similar to that described with regard to plate 85, the slots in plate 87 extending in a direction at right angles to that of the slots 83 provided in plate 85.

It is apparent from the foregoing description that I have provided a method by which cylindrical objects may be printed in a continuous operation Without hesitation or indexing. I have been able to accomplish such continuous operation by providing mechanism for placing a resilient printing pad under compression during the printing operation, the pad being maintained under compression and acting to transfer the desired image to the insulator while the insulator travels steadily through the printing station. Likewise, the printing assembly of my invention has been so constructed as to minimize wear between parts and permit ready adjustment compensation for the variables described.

While I have described my invention in terms of a preferred embodiment as shown on the drawings, it should be understood that variations thereto Will be apparent to those skilled in the art and it is submitted that such variations are within the scope of the claims which follow.

I claim:

1. In a method for transferring an image from a resilient printing pad positioned on the outer peripheral surface of a rotating wheel to spark plug insulators moving past a printing station, the steps of positioning the insulators on rotatable carrier pins mounted in spaced apart relationship on a conveyor, moving the conveyor and insulators continuously past the printing station at the desired rate, rotating the printing wheel at such a rate relative to the rate of movement of the insulators as to insure that the insulators are in position to be printed by the rotating printing pad as it passes the station, establishing contact between the insulators and the pad and maintaining such contact for a period such as to assure a complete transfer of the image, rotating the carrier pins independently of the rate of movement of the insulators past the printing station and prior to contact between the insulators and the pad to rotate the insulators at a peripheral speed substantially equal to that of the pad, and maintaining rotation of the carrier pins during contact between the insulators and the pad to substantially eliminate wear of the carrier pins and pad by the insulators.

2. In a device of the nature described, the combination comprising a printer, a rotatable Wheel on said printer, at least one resilient printing pad positioned on the outer peripheral surface of said wheel, a conveyor belt for continuously moving spark plug ceramic insulators past said printer and in printing alignment with said wheel, a plurality of carrier blocks secured to said belt, a carrier pin rotatably supported in each of said blocks and being adapted to have one of said insulators positioned on one end thereof, means for rotating said wheel at such a rate with respect to the rate of movement of said insulators past said printer as to assure contact between said pad and the insulators moving therethrough, an adjustable anvii pbsitidnedundei said conveyor belt and adjustable V with respect to said wheel to control the spacing between said pad and said insulators and thus maintain contact thereb'etwen for a period such as to" assure a complete transfer of information, means for rotating said carrier pins independently of the rate of movement of the insulators pastthe printing station and prior to and during contact between the insulators and the pad to rotate the insulators at a peripheral speed substantially equal to that of the pad to thus minimize Wear between the insul'ators and said pad and between the insulators and said carrier pins, and means for mounting said printer adjustably with respect to said conveyor belt-to perinit printing alignment therebetween; References Cited in the rile or this patefit UNITED STATES" PATENTS 

